a versatile gas injection system and an absolute calibrated spectroscopic observation system with more than 200 lines-of-sight have been installed in two divertor locations in the Wendelstein 7-X stellarator. This powerful setup enables among other measurements to infer Te and ne in the divertor region by means of line-ratio spectroscopy on thermal helium. This is a robust and routinely used diagnostic at W7-X and this work describes its main characteristics and shows some examples of Te and ne profiles. The applicability of the diagnostic is currently being extended towards the low Te and high ne conditions occurring during detachment by means of line-ratio spectroscopy on neon. Initial Te,ne profiles obtained with a neon-beam are here presented.

Fe ii emission lines are observed from nearly all classes of astronomical objects over a wide spectral range from the infrared to the ultraviolet. To meaningfully interpret these lines, reliable atomic data are necessary. In work presented here we focused on low-lying fine-structure transitions, within the ground term, due to electron impact. We provide effective collision strengths together with estimated uncertainties as functions of temperature of astrophysical importance (10 − 100, 000 K). Due to the importance of fine-structure transitions within the ground term, the focus of this work is on obtaining accurate rate coefficients at the lower end of this temperature range, for applications in low temperature environments such as the interstellar medium. We performed three different flavours of scattering calculations: i) a intermediate coupling frame transformation (ICFT) R-matrix method, ii) a Breit-Pauli (BP) R-matrix method, and iii) a Dirac R-matrix method. The ICFT and BP R-matrix calculations involved three different AUTOSTRUCTURE target models each. The Dirac R-matrix calculation was based on a reliable 20 configuration, 6069 level atomic structure model. Good agreement was found with our BP and Dirac R-matrix collision results compared to previous R-matrix calculations. We present a set of recommended effective collision strengths for the low-lying forbidden transitions together with associated uncertainty estimates.

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With the aim of providing accurate atomic data for plasma edge temperature and density modeling with neutral neon, new non-perturbative R-Matrix with Pseudostates (RMPS) calculations are performed for both the electron-impact excitation and ionization of neutral neon. The new calculations agree well with past measurements and calculations for both electron-impact excitation and ionization. For ionization, the addition of pseudostates from to allows us to extract new cross sections and rate coefficients for all of the excited states through 2p5 5p. The new RMPS ionization calculation gives a 20% increase in the cross section for the ionization compared with previous non-perturbative calculations and shows classically-expected n4-scaled convergence for the np and nd valence shells. Ionization from these excited states contributes significantly to the effective ionization rate coefficient: a factor of three more than the ground-state ionization rate coefficient at an electron temperature of 25 eV and density of 1014 cm−3. An accurate, non-perturbative set of atomic rates, both LS- and LSJ-resolved, for neutral neon across a wide range of temperatures and densities is compiled.